Endocrine Abstracts

Introduction: The Warthin-like variant of papillary thyroid cancer (WLPTC) is a rare subtype of papillary thyroid carcinoma (PTC) resembling Warthin tumours of the salivary glands, and more commonly associated with Hashimoto’s thyroiditis than other types of PTCs. The WLPTC is characterized by papillae lined by large oncocytic cells with cores having dense lymphoplasmacytic infiltrate. The prognosis of WLPTC is the same or less aggressive than that of classical PTC, but in some cases it is associated with poor outcome. The preoperative fine needle aspiration cytology (FNAC) is the most reliable technical approach for surgical decision, but it shows sometimes false negative result. The EU-TIRADS criteria (European Thyroid Association for ultrasound (US) assessment of thyroid nodules and stratification) can significantly increase diagnostic accuracy with a direct impact on treatment decisions.

Case: A 45-year-old male patient presented at outpatient clinic with Hashimoto thyroiditis for hormone replacement therapy. The first thyroid US showed an 8.1x7.6x10.4 mm irregular, hypoechoic nodule in the right lobe. A FNAC was taken from this target lesion, which resulted in a diagnosis of lymphocytic thyroiditis without suspicious malignant cells. Two years later the target nodule showed mild expansion in all dimensions: 14.4x13.2x15.7 mm. We re-assessed the following US features: non-oval shape, irregular margin, microcalcifications, marked hypo echogenicity and resulted in a EU-TIRADS 5 score. The repeated FNAC showed again a benign lymphocytic thyroiditis. Despite of the benign cytology result, thyroid lobectomy with adjunctive central lymph node dissection was recommended because of the growing tendency and high EU-TIRADS score. The histological diagnosis was WLPTC and lymphocytic thyroiditis of the nodule (pT1bN0Mx). The additional contralateral lobectomy resulted only lymphocytic thyroiditis without malignancy. Further genetic analysis is ongoing to decide on the need for the adjuvant radioiodine treatment.

Conclusion: In clinical practice, evaluation of thyroid nodules based on EU-TIRADS criteria can rarely overrule the FNAC results with an impact on surgical decision-making. In some cases, the growing tendency and the very suspicious US signs of malignancy (e.g. microcalcification) of a nodule results in a higher risk for malignancy, than that based on the FNAC results. Furthermore, in the case of WLPTC, when both the benign lymphocytic thyroiditis and malignant tumour can be seen in one nodule, the FNAC can be misleading when the aspiration is taken from the benign part of the lesion.